Lichens on a fence

I grew up in Southern California which, for all intents and purposes is a desert. Sure in California, stuff is green. But that green is at a price: water. I moved to the Seattle area almost 18 years ago and what struck me at first was how green it truly is. It's so green that moss grows on roofs. The air is really clear and healthy here thus allowing lichens to grown on a neighbor's fence.